How long has a vegetarian diet been around for?

How long has a vegetarian diet been around for?
And know any famous vegetarians?
Im doing an essay about it an any further information is also appreciated.

John A. McDougall, M.D., perhaps the most knowledgable expert on the relationship between diet and disease, asserts that our early ancestors from at least four million years ago followed diets almost exclusively of plant foods. Many other scientists believe that early humans were largely vegetarian. (See articles by Grande & Leckie and Derek Wall.) Then there’s the newest research:

Robert W. Sussman, Ph.D., professor anthropology in Arts & Sciences, spoke at a press briefing, “Early Humans on the Menu,” during the American Association for the Advancement of the Science’s Annual Meeting….
…[E]arly man was not an aggressive killer, Sussman argues. He poses a new theory, based on the fossil record and living primate species, that primates have been prey for millions of years, a fact that greatly influenced the evolution of early man.

“Our intelligence, cooperation and many other features we have as modern humans developed from our attempts to out-smart the predator,” says Sussman….

The idea of “Man the Hunter” is the generally accepted paradigm of human evolution, says Sussman, “It developed from a basic Judeo-Christian ideology of man being inherently evil, aggressive and a natural killer. In fact, when you really examine the fossil and living non-human primate evidence, that is just not the case.”

Sussman’s research is based on studying the fossil evidence dating back nearly seven million years. “Most theories on Man the Hunter fail to incorporate this key fossil evidence,” Sussman says. “We wanted evidence, not just theory. We thoroughly examined literature available on the skulls, bones, footprints and on environmental evidence, both of our hominid ancestors and the predators that coexisted with them.” …

But what Sussman and Hart discovered is that Australopithecus afarensis was not dentally pre-adapted to eat meat. “It didn’t have the sharp shearing blades necessary to retain and cut such foods,” Sussman says. “These early humans simply couldn’t eat meat. If they couldn’t eat meat, why would they hunt?”

It was not possible for early humans to consume a large amount of meat until fire was controlled and cooking was possible. Sussman points out that the first tools didn’t appear until two million years ago. And there wasn’t good evidence of fire until after 800,000 years ago.